Plasma processing apparatus and control method

ABSTRACT

Provided is a plasma processing apparatus including: a plurality of gas supply nozzles which are provided on a wall surface of a processing container and supply process gas toward the inside of the processing container in a radial direction; N microwave introducing modules of which the number disposed in a circumferential direction of a ceiling plate of the processing container so as to introduce microwaves for generating plasma into the processing container, in which N≥2; and M sensors provided on the wall surface of the processing container so as to monitor at least any one of electron density Ne and electron temperature Te of the plasma generated in the processing container, in which M equals to N or a multiple of N.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority from Japanese PatentApplication No. 2017-080620, filed on Apr. 14, 2017, with the JapanPatent Office, the disclosure of which is incorporated herein in itsentirety by reference.

TECHNICAL FIELD

The present disclosure relates to a plasma processing apparatus and acontrol method.

BACKGROUND

As one of the methods of monitoring a state of plasma, there has beenknown optical emission spectroscopy (OES) (see, e.g., Japanese PatentLaid-Open Publication No. 2016-207915). The optical emissionspectroscopy qualitatively analyzes a wavelength of an inherent brightline spectrum (atom spectrum) of an element obtained by vaporizing andexciting an object element in a sample using discharge plasma, andquantitatively analyzes light emission intensity. See, for example,Japanese Patent Laid-Open Publication Nos. 2007-294909, 2009-194032,2013-077441, and 2013-171847.

SUMMARY

To achieve the aforementioned object, according to one aspect, there isprovided a plasma processing apparatus including: a plurality of gassupply nozzles which are provided on a wall surface of a processingcontainer and supply process gas toward an inside of the processingcontainer in a radial direction; microwave introducing modules of whichthe number is N (N≥2) and which are disposed in a circumferentialdirection of a ceiling plate of the processing container so as tointroduce microwaves for generating plasma into the processingcontainer; and sensors of which the number is N or a multiple of N andwhich are provided on the wall surface of the processing container so asto monitor at least any one of electron density Ne and electrontemperature Te of the plasma generated in the processing container.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating an example of a vertical section of amicrowave plasma processing apparatus according to an exemplaryembodiment.

FIG. 2 is a view illustrating an example of an inner wall of a ceilingplate of the microwave plasma processing apparatus according to theexemplary embodiment.

FIG. 3 is a view illustrating an example of a configuration of amicrowave plasma source according to the exemplary embodiment.

FIG. 4 is a view illustrating an example of an arrangement configurationof probes and gas supply nozzles according to the exemplary embodiment.

FIG. 5 is a view illustrating an example of power dependency of electrondensity of plasma measured by probes according to the exemplaryembodiment.

FIG. 6 is a view illustrating an example of power dependency of anelectron temperature of the plasma measured by probes according to theexemplary embodiment.

FIGS. 7A to 7D are views illustrating examples of mounting positions ofprobes according to the exemplary embodiment.

FIG. 8 is a view illustrating an example of a measurement result by theprobes at the mounting positions of the probes illustrated in FIGS. 7Ato 7D.

FIGS. 9A to 9D are views illustrating modified examples of the mountingpositions of the probe according to the exemplary embodiment.

FIG. 10 is a view illustrating an example of a measurement result by theprobes at the mounting positions of the probes illustrated in FIGS. 9Ato 9D.

FIG. 11 is a flowchart illustrating an example of a process ofcontrolling microwaves in accordance with the measurement result by theprobes according to the exemplary embodiment.

DESCRIPTION OF EMBODIMENT

In the following detailed description, reference is made to theaccompanying drawing, which form a part hereof. The illustrativeembodiments described in the detailed description, drawing, and claimsare not meant to be limiting. Other embodiments may be utilized, andother changes may be made without departing from the spirit or scope ofthe subject matter presented here.

In the optical emission spectroscopy, it is impossible to monitor thedistribution of plasma because the overall state of the plasma ismonitored. In addition, in the optical emission spectroscopy,wavelengths of light emission spectrums of different gas excited speciesoverlap one another in some instances in a case in which multiple typesof gases are supplied into a processing container, and as a result,accuracy in monitoring plasma characteristics may be insufficient.

Meanwhile, microwaves need to be controlled for each microwaveintroducing module when microwaves are introduced into the processingcontainer from the plurality of microwave introducing modules. For thisreason, it is important to ascertain a distribution of plasma.

In regard to the problems described above, in one aspect, an object ofthe present disclosure is to monitor a distribution of plasma.

To achieve the aforementioned object, according to one aspect of thepresent disclosure, there is provided a plasma processing apparatusincluding: a plurality of gas supply nozzles which are provided on awall surface of a processing container and supply process gas toward theinside of the processing container in a radial direction; N microwaveintroducing modules of which the number disposed in a circumferentialdirection of a ceiling plate of the processing container so as tointroduce microwaves for generating plasma into the processingcontainer, in which N≥2; and M sensors provided on the wall surface ofthe processing container so as to monitor at least any one of electrondensity Ne and electron temperature Te of the plasma generated in theprocessing container, in which M equals to N or a multiple of N.

In the above-described plasma processing apparatus, the M sensors areprovided at a height equal to or lower than a height of the plurality ofgas supply nozzles and protrude in a horizontal direction, an obliquedirection, or a vertical direction toward the inside of the processingcontainer in the radial direction.

In the above-described plasma processing apparatus, the M sensors areprovided at a height higher than a height of the multiple gas supplynozzles, and protrude in a horizontal direction toward the inside of theprocessing container in the radial direction or are disposed in a stateof being embedded in the wall surface of the processing container.

In the above-described plasma processing apparatus, the M sensors areprobes that protrude from the wall surface of the processing containertoward the inside of the processing container in the radial direction.

In the above-described plasma processing apparatus, the M probes arecoated with an insulating material.

In the above-described plasma processing apparatus, the M sensors aredisposed at regular intervals in the circumferential direction.

In the above-described plasma processing apparatus, the plurality of gassupply nozzles and the M sensors are provided at the same height.

In the above-described plasma processing apparatus, the M sensors areprovided at the same height ranging from −10 mm to 80 mm in a verticaldirection from a surface of a placement table on which a workpiece isplaced in the processing container.

In the above-described plasma processing apparatus, the plurality of gassupply nozzles and the M sensors provided at different heights.

In the above-described plasma processing apparatus, the M sensors aredisposed at positions symmetrical with respect to positions of the Nmicrowave introducing modules disposed at regular intervals on theceiling plate of the processing container based on a central axis of theprocessing container.

According to another aspect of the present disclosure, there is provideda method of controlling plasma using a plasma processing apparatus. Theplasma processing apparatus includes a plurality of gas supply nozzleswhich are provided on a wall surface of a processing container andsupply process gas toward the inside of the processing container in aradial direction, N microwave introducing modules disposed in acircumferential direction of a ceiling plate of the processing containerso as to introduce microwaves for generating plasma into the processingcontainer, in which N≥2, and M sensors provided on the wall surface ofthe processing container so as to monitor electron density Ne andelectron temperature Te of the plasma generated in the processingcontainer, in which M equals to N or a multiple of N. The methodincludes: controlling at least any one of power of the microwavesintroduced from the microwave introducing modules and a phase of themicrowaves introduced from the microwave introducing modules based on atleast any one of the electron density Ne and the electron temperature Teof the plasma monitored by the sensors.

According to one aspect, it is possible to monitor a distribution ofplasma.

Hereinafter, an exemplary embodiment of the present disclosure will bedescribed with reference to the drawings. Further, in the presentspecification and the drawings, substantially identical configurationsare denoted by the same reference numerals, and a repeated descriptionthereof will be omitted.

<Microwave Plasma Processing Apparatus>

FIG. 1 illustrates an example of a cross-sectional view of a microwaveplasma processing apparatus 100 according to an exemplary embodiment ofthe present disclosure. The microwave plasma processing apparatus 100has a chamber 1 which accommodates a wafer W. The microwave plasmaprocessing apparatus 100 is an example of a plasma processing apparatusfor performing a predetermined plasma process on a semiconductor wafer W(hereinafter, referred to as a “wafer W”) using surface wave plasmaformed by microwaves on a chamber 1 side surface. A deposition processor an etching process is performed as an example of the predeterminedplasma process.

The chamber 1 is a substantially cylindrical processing containerconfigured in a gastight manner and made of a metallic material such asaluminum or stainless steel. The chamber 1 is grounded. A microwaveplasma source 2 is provided to face the inside of the chamber 1 fromopenings 1 a formed in an inner wall of a ceiling plate of the chamber1. When the microwaves are introduced into the chamber 1 from themicrowave plasma source 2 through the openings 1 a, the surface waveplasma is formed in the chamber 1.

A placement table 11 on which the wafer W is placed is provided in thechamber 1. The placement table 11 is supported by a cylindrical supportmember 12 provided vertically in the center of the bottom portion of thechamber 1 through an insulating member 12 a. As an example, a material,which constitutes the placement table 11 and the support member 12, is ametal such as aluminum of which the surface is subjected to an alumitetreatment (anodic oxidizing treatment) or an insulating member (ceramicsor the like) having therein a high-frequency electrode. The placementtable 11 may be provided with an electrostatic chuck forelectrostatically holding the wafer W, a temperature control mechanism,and a gas flow path for supplying heat transfer gas to a rear surface ofthe wafer W.

The placement table 11 is electrically connected to a high-frequencybias power source 14 through a matching device 13. Ions in the plasmaare introduced to the wafer W side as high-frequency power is suppliedto the placement table 11 from the high-frequency bias power source 14.Further, the high-frequency bias power source 14 may not be provided inaccordance with characteristics of the plasma process.

A gas discharge pipe 15 is connected to the bottom portion of thechamber 1, and a gas discharge device 16, which includes a vacuum pump,is connected to the gas discharge pipe 15. When the gas discharge device16 operates, gas in the chamber 1 is discharged such that pressure inthe chamber 1 is decreased at a high speed to a predetermined degree ofvacuum. A loading and unloading port 17 for loading and unloading thewafer W and a gate valve 18 for opening and closing the loading andunloading port 17 are provided on the sidewall of the chamber 1.

The microwave plasma source 2 has a microwave output unit 30, microwavetransmitting units 40, and microwave radiating members 50. The microwaveoutput unit 30 outputs and distributes the microwaves to a plurality ofpaths.

The microwave transmitting unit 40 transmits the microwaves output fromthe microwave output unit 30. Circumferential edge microwave introducingmechanisms 43 a and a central microwave introducing mechanism 43 b,which are provided in the microwave transmitting units 40, serve tointroduce the microwaves output from amplifier units 42 to the microwaveradiating members 50 and to match impedance.

The circumferential edge microwave introducing mechanisms 43 a and thecentral microwave introducing mechanism 43 b each have a cylindricalouter conductor 52 and a bar-shaped inner conductor 53 provided in thecenter of the cylindrical outer conductor 52, and the cylindrical outerconductor 52 and the bar-shaped inner conductor 53 are coaxiallydisposed. A microwave transmitting path 44, through which microwavepower is supplied and the microwaves are transmitted toward themicrowave radiating member 50, is provided between the outer conductor52 and the inner conductor 53.

The circumferential edge microwave introducing mechanisms 43 a and thecentral microwave introducing mechanism 43 b each have slugs 61, and animpedance adjusting member 140 positioned at a tip end portion thereof.As the slugs 61 are moved, the impedance of a load (plasma) in thechamber 1 are matched with characteristic impedance of microwave powerof the microwave output unit 30. The impedance adjusting member 140 ismade of a dielectric material such that the impedance of the microwavetransmitting path 44 is adjusted in accordance with a relativedielectric constant of the impedance adjusting member 140.

The microwave radiating member 50 is provided to be sealed in a gastightmanner in a support ring 129 provided at an upper side of the chamber 1,and radiates microwaves, which are output from the microwave output unit30 and transmitted from the microwave transmitting unit 40, into thechamber 1. The microwave radiating member 50 constitutes the ceilingportion of the chamber 1.

The microwave radiating member 50 has a main body portion 120, slow-wavemembers 121 and 131, microwave transmitting members 122 and 132, slots123 and 133, and dielectric layers 124. The main body portion 120 ismade of a metal.

The main body portion 120 has six circumferential edge microwaveintroducing mechanisms 43 a and one central microwave introducingmechanism 43 b. As illustrated in FIG. 2, the six circumferential edgemicrowave introducing mechanisms 43 a are disposed in thecircumferential direction of the ceiling plate of the chamber 1. Thesingle central microwave introducing mechanism 43 b is disposed at acenter of the ceiling plate of the chamber 1.

Referring back to FIG. 1, the slow-wave member 121 is fitted into themain body portion 120 so as to correspond to the circumferential edgemicrowave introducing mechanism 43 a, and the wave delay member 131 isfitted into the main body portion 120 so as to correspond to the centralmicrowave introducing mechanism 43 b. The slow-wave members 121 and 131are formed as disk-shaped dielectric members that transmit themicrowaves. The slow-wave members 121 and 131 have a relative dielectricconstant higher than that of the vacuum, and for example, may be made ofceramics such as quartz or alumina (Al₂O₃), a fluorine-based resin suchas polytetrafluoroethylene, or a polyimide-based resin. Because thewavelength of microwaves is increased in vacuum, the slow-wave members121 and 131 are made of a material having a relative dielectric constanthigher than that of the vacuum, and as a result, the slow-wave members121 and 131 serve to decrease a size of an antenna including the slots123 and 133 by decreasing the wavelength of the microwaves.

Below the slow-wave members 121 and 131, the disk-shaped microwavetransmitting members 122 and 132 are fitted into the main body portion120. The slot 123 and the dielectric layer 124 are formed between theslow-wave member 121 and the microwave transmitting member 122 such thatthe slow-wave member 121, the slot 123, the dielectric layer 124, andthe microwave transmitting member 122 are formed in this order from theupper side thereof. The slot 133 is formed in the main body portion 120between the slow-wave member 131 and the microwave transmitting member132.

The microwave transmitting members 122 and 132 are made of a dielectricmaterial that transmits microwaves. FIG. 2 illustrates an example of aninner wall of the ceiling plate of the microwave plasma processingapparatus 100 according to the exemplary embodiment. Gas supply holesare omitted from FIG. 2.

In the present exemplary embodiment, six microwave transmitting members122, which correspond to six circumferential edge microwave introducingmechanisms 43 a, are disposed at regular intervals in thecircumferential direction of the main body portion 120, and exposed in acircular shape to the inside of the chamber 1. In addition, the singlemicrowave transmitting member 132, which corresponds to the centralmicrowave introducing mechanism 43 b, is exposed in a circular shapetoward the inside of the chamber 1 at the center of the chamber 1.

The microwave transmitting members 122 and 132 serve as dielectricwindows for forming surface wave plasma uniform in the circumferentialdirection. For example, similar to the slow-wave members 121 and 131,the microwave transmitting members 122 and 132 may be made of ceramicssuch as quartz or alumina (Al₂O₃), a fluorine-based resin such aspolytetrafluoroethylene, or a polyimide-based resin.

In the present exemplary embodiment, the number of circumferential edgemicrowave introducing mechanisms 43 a is six, but the number ofcircumferential edge microwave introducing mechanisms 43 a is notlimited thereto, and N circumferential edge microwave introducingmechanisms 43 a are disposed. N may be two or more, and may particularlybe three or more, and for example, N may be three to six. Further, themicrowave radiating members 50 are an example of N (N≥2) microwaveintroducing modules which are disposed in the circumferential directionof the ceiling plate of the chamber 1 and introduce the microwaves forgenerating plasma into the processing container.

Referring back to FIG. 1, the microwave radiating members 50 areprovided with first gas introducing units 21 having a shower structure,and a first gas supply source 22 is connected to the first gasintroducing units 21 through gas supply pipes 111. A first gas, which issupplied from the first gas supply source 22, is supplied in the form ofa shower into the chamber 1 through the first gas introducing units 21.The first gas introducing unit 21 is an example of a first gas showerhead which supplies the first gas at a first height from a plurality ofgas holes formed in the ceiling portion of the chamber 1. Examples ofthe first gas may include, for example, a gas such as Ar gas forgenerating plasma, or for example, a gas such as O₂ gas or N₂ gas to bedecomposed by high energy.

Gas supply nozzles 27, which are an example of second gas introducingunits, are provided horizontally in the chamber 1 at positions in thechamber 1 between the placement table 11 and the microwave radiatingmembers 50. The gas supply nozzles 27 are connected to gas supply pipes28 a formed in ring-shaped members 28 fitted into the sidewall of thechamber 1, and a second gas supply source 29 is connected to the gassupply pipes 28 a. A second gas such as, for example, SiH₄ gas or C₅F₈gas, which is a process gas to be supplied without being decomposed tothe utmost, is supplied from the second gas supply source 29 during theplasma process such as the deposition process or the etching process.The gas supply nozzles 27 supply the second gas from a plurality of gasholes at a height lower than the height of the plurality of gas holesthrough which the first gas is supplied from the first gas supply source22. Further, various types of gases may be used as the gases to besupplied from the first gas supply source 22 and the second gas supplysource 29 in accordance with the contents of the plasma process.

Respective parts of the microwave plasma processing apparatus 100 arecontrolled by a control device 3. The control device 3 has amicroprocessor 4, a read only memory (ROM) 5, and a random access memory(RAM) 6. The ROM 5 or the RAM 6 stores a process sequence of themicrowave plasma processing apparatus 100 and a process recipe which isa control parameter. The microprocessor 4 is an example of a controllerwhich controls the respective parts of the microwave plasma processingapparatus 100 based on the process sequence and the process recipe. Inaddition, the control device 3 has a touch panel 7 and a display 8, andmay display an input or a result when performing predetermined controlaccording to the process sequence and the process recipe.

When the microwave plasma processing apparatus 100 having such aconfiguration performs the plasma process, a wafer W is first loadedinto the chamber 1 through the loading and unloading port 17 from theopened gate valve 18 in a state in which the wafer W is held on atransfer arm. The gate valve 18 is closed after the wafer W is loaded.When the wafer W is transferred to a position above the placement table11, the wafer W is transferred from the transfer arm to pusher pins andplaced on the placement table 11 as the pusher pins move downward. Thepressure in the chamber 1 is maintained to a predetermined degree ofvacuum by the gas discharge device 16. The first gas is introduced inthe form of a shower into the chamber 1 from the first gas introducingunits 21, and the second gas is introduced in the form of a shower intothe chamber 1 from the gas supply nozzle 27. The first gas and thesecond gas are decomposed by the microwaves radiated from the microwaveradiating members 50 through the circumferential edge microwaveintroducing mechanisms 43 a and the central microwave introducingmechanism 43 b such that the plasma process is performed on the wafer Wby the surface wave plasma generated on the surface at the side of thechamber 1.

<Microwave Plasma Source>

As illustrated in FIG. 3, the microwave output unit 30 of the microwaveplasma source 2 has a microwave power source 31, a microwave oscillator32, an amplifier 33 which amplifies a generated microwave, and adistributor 34 which distributes the amplified microwave to a pluralityof microwaves.

The microwave oscillator 32 generates microwaves having a predeterminedfrequency through, for example, a phase locked loop (PLL). Thedistributor 34 distributes the microwaves amplified by the amplifier 33while matching the input side impedance and the output side impedance soas to inhibit a loss of microwaves to the utmost. Further, various typesof frequencies ranging from 700 MHz to 3 GHz may be used as thefrequency of the microwaves.

The microwave transmitting unit 40 has the plurality of amplifier units42, and the circumferential edge microwave introducing mechanisms 43 aand the central microwave introducing mechanism 43 b which are providedto correspond to the amplifier units 42. The amplifier units 42 guidethe microwaves, which are distributed by the distributor 34, to thecircumferential edge microwave introducing mechanisms 43 a and thecentral microwave introducing mechanism 43 b. The amplifier unit 42 hasa phase shifter 46, a variable gain amplifier 47, a main amplifier 48which constitutes a solid state amplifier, and an isolator 49.

The phase shifter 46 may modulate radiation characteristics by changingthe phases of the microwaves. For example, it is possible to change aplasma distribution by controlling directivity by adjusting the phasesof the microwaves introduced to the circumferential edge microwaveintroducing mechanisms 43 a and the central microwave introducingmechanism 43 b. In addition, it is possible to obtain circularlypolarized waves by shifting the phases of the adjacent microwaveintroducing mechanisms by 90°. In addition, the phase shifter 46 may beused for the purpose of space synthesis in a tuner by adjusting delaycharacteristics between components in the amplifier. However, the phaseshifter 46 may not be provided when it is not necessary to adjust theradiation characteristics or to adjust delay characteristics between thecomponents in the amplifier need to be modulated.

The variable gain amplifier 47 adjusts plasma intensity by adjusting apower level of the microwave input to the main amplifier 48. Thevariable gain amplifier 47 is changed for each antenna module such thata distribution of the generated plasma occurs.

For example, the main amplifier 48, which constitutes a solid stateamplifier, has an input matching circuit, a semiconductor amplifierelement, an output matching circuit, and a high-Q resonance circuit. Theisolator 49 is configured to separate reflective microwaves which arereflected by a slot antenna unit and directed toward the main amplifier48, and the isolator 49 has a circulator and a dummy load (coaxialterminator). The circulator guides the reflected microwaves to the dummyload, and the dummy load converts the reflective microwaves, which isguided by the circulator, into heat. The circumferential edge microwaveintroducing mechanisms 43 a and the central microwave introducingmechanism 43 b introduce the microwaves output from the amplifier units42 to the microwave radiating members 50.

<Probe>

As illustrated in FIG. 1, in the microwave plasma processing apparatus100 according to the present exemplary embodiment, probes 80 areprovided at the same height as the gas supply nozzle 27. FIG. 4 is aperspective view illustrating a part of an arrangement configuration ofthe probes 80 and the gas supply nozzles 27 according to the exemplaryembodiment.

The probes 80 are provided on the wall surface of the chamber 1 andprotrude inward in a radial direction of the chamber 1 from the wallsurface of the chamber 1. The number of probes 80 is six or a multipleof six.

In the present exemplary embodiment, six probes are disposed tocorrespond to the circumferential edge microwave introducing mechanisms43 a one by one with respect to six circumferential edge microwaveintroducing mechanisms 43 a disposed at regular intervals on the ceilingplate of the chamber 1 and the six microwave transmitting members 122illustrated in FIG. 2.

However, the number of probes 80 is not limited thereto, and when thenumber of circumferential edge microwave introducing mechanisms 43 a isN, the probes 80 of which the number is N or a multiple of N may bedisposed at positions symmetrical with respect to the positions of the Nmicrowave radiating members 50 (N microwave transmitting members 122)which are disposed at regular intervals on the ceiling plate of thechamber 1, based on the central axis O of the chamber 1.

The number of gas supply nozzles 27 is not particularly limited. In thepresent exemplary embodiment, the number of gas supply nozzles 27 iseighteen, and the gas supply nozzles 27 are disposed at regularintervals in the circumferential direction so that each of the gassupply nozzles 27 is disposed between two probes 80. As described above,the probes 80 and the gas supply nozzles 27 may be disposed at the sameheight. However, the probes 80 and the gas supply nozzles 27 may bedisposed at different heights. In addition, the probes 80 and the gassupply nozzles 27 may be disposed in the circumferential direction ofthe chamber 1 at the positions symmetrical with respect to the positionsof the N microwave radiating members 50 (N microwave transmittingmembers 122), based on the central axis O of the chamber 1.

Each of the probes 80 monitors electron density Ne of plasma or electrontemperature Te of plasma. For example, each probe 80 may have a metallicportion coated with an insulating material such as alumina (Al₂O₃).Therefore, it is possible to avoid the occurrence of metal contaminationcaused by the probes 80 in the chamber 1 during the plasma process,thereby inhibiting the occurrence of particles.

When voltage with sine waves is applied to the probes 80 under thecontrol of the control device 3, a measuring device 81 measures electriccurrent flowing through the probes 80 during the plasma process. Theelectric current flowing through the probes 80 is equivalent to anelectric current flowing through the plasma generated in the chamber 1.The measuring device 81 transmits a signal, which indicates a waveformof the measured electric current, to the control device 3. Themicroprocessor 4 of the control device 3, which has received the signal,analyzes the waveform of the electric current included in the signal bytransforming the waveform of the electric current through Fouriertransform, thereby calculating the electron density Ne and the electrontemperature Te of the plasma. Therefore, the distribution of the plasmain the circumferential direction below six circumferential edgemicrowave introducing mechanisms 43 a may be monitored by six probes 80.

Based on the electron density Ne and the electron temperature Te of theplasma which are calculated based on the measurement result obtained byusing the probes 80, the microprocessor 4 controls, in real time duringthe plasma process, power of the microwaves introduced into the chamber1 from the circumferential edge microwave introducing mechanisms 43 athat correspond to the probes 80 used for the calculation. Specifically,based on the calculated electron density Ne and the calculated electrontemperature Te of the plasma, the microprocessor 4 adjusts power levelsof the microwaves input to the main amplifiers 48 by controlling thevariable gain amplifiers 47 of the amplifier units 42 which output themicrowaves to the corresponding circumferential edge microwaveintroducing mechanisms 43 a. Therefore, the plasma distribution ischanged by adjusting the plasma intensity of the microwaves to beintroduced into the corresponding circumferential edge microwaveintroducing mechanisms 43 a.

Based on the calculated electron density Ne and the calculated electrontemperature Te of the plasma, the microprocessor 4 controls, in realtime, the phases of the microwaves to be transmitted to thecircumferential edge microwave introducing mechanisms 43 a whichcorrespond to the probes 80 used for the calculation. Specifically,based on the calculated electron density Ne and the calculated electrontemperature Te of the plasma, the microprocessor 4 adjusts radiationcharacteristics by changing the phases of the microwaves by controllingthe phase shifters 46 of the amplifier units 42 which output themicrowaves to the corresponding circumferential edge microwaveintroducing mechanisms 43 a. Therefore, the plasma distribution ischanged by controlling directivity by adjusting the phases of themicrowaves to be introduced into the corresponding circumferential edgemicrowave introducing mechanisms 43 a.

As described above, in the present exemplary embodiment, the power ofthe microwave and the phase of the microwave are controlled, but atleast any one of the power of the microwave and the phase of themicrowave may be controlled. However, both of the power of the microwaveand the phase of the microwave may be controlled.

A graph of FIG. 5 illustrates an example of a result of comparing powerdependency of electron density Ne of plasma measured by the probes 80according to the present exemplary embodiment with power dependency ofelectron density Ne measured by a Langmuir probe of a comparativeexample. According to the present graph, it can be seen that the powerdependency of the electron density Ne of the plasma measured by theprobes 80 according to the present exemplary embodiment almost coincideswith the power dependency of the electron density Ne of the plasmameasured by Langmuir probes.

The graph of FIG. 6 illustrates an example of a result of comparingpower dependency of electron temperature Te of plasma measured by theprobes 80 according to the present exemplary embodiment with powerdependency of electron temperature Te measured by Langmuir probes of thecomparative example. According to this graph, it can be seen that thepower dependency of the electron temperature Te of the plasma measuredby the probes 80 according to the present exemplary embodiment almostcoincides with the power dependency of the electron temperature Te ofthe plasma measured by the Langmuir probes.

That is, the result of measuring electrical characteristics of plasmaillustrates that the probes 80 according to the present exemplaryembodiment and the Langmuir probes have almost the same characteristics,and as a result, it can be confirmed that the probes 8 according to thepresent exemplary embodiment performs almost the same function as theLangmuir probes. Further, an example of measuring electricalcharacteristics of plasma using the Langmuir probes is disclosed inJapanese Patent Application Laid-Open No. 2009-194032.

As described above, according to the plasma processing apparatusaccording to the present exemplary embodiment, the plasma iselectrically measured by the N probes 80 which are provided in thechamber 1, and as a result, it is possible to monitor a distribution ofthe plasma and characteristics of the plasma. Therefore, it is possibleto control the distribution of the plasma and uniformity of the plasma,and as a result, it is possible to reduce time and costs required tooptimize the process.

<Mounting Position of Probe>

Next, mounting positions of the probes 80 will be described withreference to FIGS. 7A to 7D to FIG. 10. FIGS. 7A to 7D illustrateexamples of mounting positions of the probes 80 according to theexemplary embodiment. FIG. 8 illustrates an example of a measurementresult by the probes 80 at the mounting positions of the probes 80 inFIGS. 7A to 7D.

FIG. 7A illustrates a case in which a probe 80 is mounted to protrudefrom the sidewall of the chamber 1 at a position at a height (H1=53 mm)from a surface of the placement table 11 when the surface of theplacement table 11 is at a height of 0 mm FIG. 7B illustrates a case inwhich a probe 80 is mounted to protrude from the sidewall of the chamber1 at a position at a height (H2=33 mm) from the surface of the placementtable 11.

FIG. 7C illustrates a case in which a probe 80 is mounted to protrudefrom the sidewall of the chamber 1 at a position at a height (H3=13 mm)from the surface of the placement table 11. FIG. 7D illustrates a casein which a probe 80 is mounted to protrude from the sidewall of thechamber 1 at a position at a height (H4=−7 mm) from the surface of theplacement table 11 (i.e., at a position slightly lower than the surfaceof the placement table 11).

All of FIGS. 7A to 7D illustrate that a gas supply nozzle 27 and a probe80 are provided at the same height.

FIG. 8 illustrates a distribution of electron density Ne of plasma inthe radial direction on the surface of the wafer W which is calculatedat the mounting positions in FIGS. 7A to 7D based on waveforms ofelectric currents measured using the probes 80. A horizontal axisindicates a diameter of the wafer W, a left end (R=0 mm) of thehorizontal axis indicates a center of the wafer, and a right end (R=150mm) thereof indicates an end of the wafer W. A vertical axis indicateselectron density Ne of plasma.

According to the distribution, it can be seen that since all the probes80 at the mounting positions in FIGS. 7A to 7D behave similarly, thedistribution of plasma is measured. That is, it can be seen that themounting positions of the probes 80 in a height direction may be anyposition. However, the electron density Ne of the plasma at the end ofthe wafer W is increased as the mounting positions of the probes 80 arelowered such that the distribution state of plasma coincides with anactual distribution state of plasma. Therefore, as the mountingpositions of the probes 80 are lowered, the measurement result by theprobes 80 becomes favorable.

A position for supplying gas needs to be set in consideration of thediffusion of a gas or a position of the wafer W, in order to supply thegas into a space for generating plasma in a case in which the gas supplynozzles 27 and the probes 80 are provided at different heights as wellas in the case in which the gas supply nozzles 27 and the probes 80 areprovided at the same height. In view of the foregoing, in any case, theheight of the probes 80 needs to be within the range from −10 mm to 80mm when the height of the surface of the placement table 11 is 0 mm.

However, there are the following advantages when the heights of the gassupply nozzles 27 and the probes 80 are equal to each other. That is,when the probes 80 are provided below the gas supply nozzles 27, theamount of electric current flowing through the probes 80 is smaller thanthe amount of electric current flowing through the plasma such thatplasma density Ne obtained as a measurement result is decreased, and asa result, measurement accuracy may deteriorate. However, but when theheights of the gas supply nozzles 27 and the probes 80 are equal to eachother, such concern is avoided.

In the present exemplary embodiment, the gas supply nozzles 27, theprobes 80, and the microwave radiating members 50 have structuralsymmetry, and as a result, it is possible to further improve monitoringaccuracy of the probes 80.

FIGS. 9A to 9D illustrate other examples of the mounting positions ofthe probes 80 according to the exemplary embodiment. FIG. 10 illustratesan example of a measurement result by the probes 80 at the mountingpositions of the probes 80 in FIGS. 9A to 9D. FIG. 9A has the samecondition as FIG. 7A, and the height of the gas supply nozzle 27 and theheight of the probe 80 are equal to each other.

FIG. 9B illustrates a case in which a probe 80 is mounted to protrude inan oblique direction from a corner of the bottom surface of the chamber1. The gas supply nozzle 27 and the probe 80 are mounted at the sameheight and in the same direction. FIG. 9C illustrates a case in which aprobe 80 is mounted to protrude in a vertical direction from the bottomsurface of the chamber 1. The gas supply nozzle 27 and the probe 80 aremounted in the same direction from the same position.

FIG. 10 illustrates a distribution of electron density Ne of plasma inthe radial direction on the surface of the wafer W which is calculatedat the mounting positions in FIGS. 9A to 9C based on waveforms ofelectric current measured by using the probes 80. The horizontal axisand the vertical axis are identical to those in FIG. 8.

According to the distribution, all of the probes 80 behave similarly,and the electron density Ne of the plasma tends to be decreased towardthe end of the wafer W, but the distribution of the plasma is measured.From the results described above, it can be seen that any of themounting positions and any of the mounting angles of the probes 80illustrated in FIGS. 9A to 9C are good.

In view of the foregoing, in the case in which the probes 80 areprovided at a height equal to the height of the gas supply nozzles 27 orprovided at a height lower than the height of the gas supply nozzles 27,the probes 80 may protrude from the side surface or the bottom surfaceof the chamber 1 in the horizontal direction, the oblique direction, orthe vertical direction toward the inside of the chamber 1 in the radialdirection. In this case, the tips of six probes 80 are provided at thesame height ranging from −10 mm to 80 mm in the vertical direction fromthe surface (0 mm) of the placement table 11.

FIG. 9D illustrates a variation in a case in which probes 80 ishorizontally provided at heights different from the height of the gassupply nozzle 27. In this case, the probes 80 may be mounted at aposition lower than the gas supply nozzle 27. However, six probes 80 areprovided at the same height ranging from −10 mm to 80 mm in the verticaldirection from the surface (0 mm) of the placement table 11.

A probe 80′ is a probe 80 which is mounted at a position higher than theplurality of gas supply nozzles 27, and a dash is conveniently added tothe reference numeral of the probe 80 in order to distinguish the probe80′ from the probes 80 mounted at the other positions. The probe 80′ maybe disposed at a portion where plasma P is less present. For thisreason, the probe 80′, which is mounted at the position higher than theplurality of gas supply nozzles 27, has a shorter radial length than theplurality of gas supply nozzles 27. To prevent an interference with theplasma P, the probe 80′ may have a shorter radial length as the heightat which the probe 80′ is disposed is increased.

For example, a sensor 80″ is embedded in a wall surface of the chamber 1such that the tip end of the sensor 80″ is exposed from a surfaceidentical to the wall surface of the chamber 1, but the sensor 80″ doesnot protrude from the wall surface of the chamber 1. As described above,in the present exemplary embodiment, the sensor, which monitors theelectron density Ne and the electron temperature Te of the plasmagenerated in the chamber 1, is not limited to the probe 80 and the probe80′, but may be the sensor 80″.

<Real Time Control>

Lastly, an example of a real time process of controlling microwaves inaccordance with a measurement result by the probes 80 of the microwaveplasma processing apparatus 100 according to the present exemplaryembodiment will be described with reference to a flowchart of FIG. 11.The present process is mainly performed by the microprocessor 4 of thecontrol device 3.

When the present process is initiated, the microprocessor 4 determineswhether an output of microwaves and a supply of gas are initiated (stepS10).

When the microprocessor 4 determines that the output of the microwavesand the supply of the gas are initiated, the microprocessor 4 appliesvoltage to the six probes 80 (step S12). Next, the microprocessor 4 setsa variable N to “0” (step S14).

Next, the microprocessor 4 adds “1” to the variable N (step S16). Themeasuring device 81 measures electric current flowing through the N^(th)probe 80, and transmits a signal indicating the measurement result tothe control device 3 (step S18).

The microprocessor 4 receives the signal from the measuring device 81,and acquires a waveform of the electric current indicated by the signal.The microprocessor 4 calculates the electron density Ne of the plasmaand the electron temperature Te of the plasma by analyzing the acquiredwaveform of the electric current by transforming the acquired waveformof the electric current through Fourier transform (step S20). Therefore,it is possible to monitor a distribution of plasma in thecircumferential direction at a position below one circumferential edgemicrowave introducing mechanism 43 a which is specified by a used probe80 among the six circumferential edge microwave introducing mechanisms43 a.

Next, based on the calculated electron density Ne and the calculatedelectron temperature Te of the plasma, the microprocessor 4 may control,in real time, the power of the microwave introduced into the chamber 1from the circumferential edge microwave introducing mechanism 43 acorresponding to the probe 80 used for the measurement. In addition, themicroprocessor 4 may control, in real time, the phase of the microwavetransmitted from the corresponding circumferential edge microwaveintroducing mechanism 43 a.

Next, the microprocessor 4 determines whether the variable N is six ormore (step S24). When the variable N is less than six, themicroprocessor 4 determines that the measurement by all the probes 80 isnot completed, and the process goes back to step S16, and steps S16 toS24 are repeated. Meanwhile, when the variable N is six or more, themicroprocessor 4 determines that the measurement by all the probes 80 iscompleted, and determines whether the output of the microwave and thesupply of the gas are stopped (step S26). When the microprocessor 4determines that the output of the microwave and the supply of the gasare not stopped, the process goes back to step S14, the variable N isinitialized (step S14), and the subsequent processes are repeated.Meanwhile, when the microprocessor 4 determines that the output of themicrowave and the supply of the gas are stopped, the present processends.

As described above, according to the microwave plasma processingapparatus 100 of the present exemplary embodiment, the electron densityNe of the plasma and the electron temperature Te of the plasma aremonitored by the probes 80, thereby ascertaining the distribution of theplasma and the characteristics of the plasma.

Therefore, based on the electron density Ne of the plasma and theelectron temperature Te of the plasma, at least any one of the power ofthe introduced microwave and the phase of the introduced microwave maybe controlled in real time. As a result, it is possible to improveuniformity of plasma.

Based on the electron density Ne of the plasma or the electrontemperature Te of the plasma, at least any one of the power of theintroduced microwave and the phase of the introduced microwave may becontrolled in real time. Even in this case, it is possible to improveuniformity of plasma.

For example, the microwave plasma processing apparatus according to thepresent disclosure may monitor a film thickness. Specifically, a film isformed on the probe during the plasma process, and as a result, awaveform of an electric current flowing through the respective probes,which is measured by the measuring device, is changed. Therefore, thecontrol device of the microwave plasma processing apparatus according tothe present disclosure may estimate a thickness of a film attached tothe probe by analyzing a change in intensity of the signals acquiredfrom the respective probes. Therefore, it is possible to ascertain astate in the chamber 1.

According to the microwave plasma processing apparatus according to thepresent disclosure, it is possible to ascertain an energy distributionof kinetic energy of electrons by using an electric energy distributionfunction (EEDF).

Herein, the semiconductor wafer W has been described as an example of aworkpiece. However, the workpiece is not limited thereto, and varioustypes of substrates may be used for a liquid crystal display (LCD) or aflat panel display (FPD), a photo mask, a CD substrate, a printedsubstrate, and the like.

From the foregoing, it will be appreciated that various embodiments ofthe present disclosure have been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the various embodiments disclosed herein are not intendedto be limiting, with the true scope and spirit being indicated by thefollowing claims.

What is claimed is:
 1. A plasma processing apparatus comprising: aplurality of gas supply nozzles which are provided on a wall surface ofa processing container and supply process gas toward an inside of theprocessing container in a radial direction; N microwave introducingmodules disposed in a circumferential direction of a ceiling plate ofthe processing container so as to introduce microwaves for generatingplasma into the processing container, wherein N≥2; and M sensorsprovided on the wall surface of the processing container so as tomonitor at least any one of electron density Ne and electron temperatureTe of the plasma generated in the processing container, wherein M equalsto N or a multiple of N.
 2. The plasma processing apparatus according toclaim 1, wherein the M sensors are provided at a height equal to orlower than a height of the plurality of gas supply nozzles and protrudein a horizontal direction, an oblique direction, or a vertical directiontoward the inside of the processing container in the radial direction.3. The plasma processing apparatus according to claim 1, wherein the Msensors are provided at a height higher than a height of the multiplegas supply nozzles, and protrude in a horizontal direction toward theinside of the processing container in the radial direction or aredisposed in a state of being embedded in the wall surface of theprocessing container.
 4. The plasma processing apparatus according toclaim 1, wherein the M sensors are probes that protrude from the wallsurface of the processing container toward the inside of the processingcontainer in the radial direction.
 5. The plasma processing apparatusaccording to claim 4, wherein the M probes are coated with an insulatingmaterial.
 6. The plasma processing apparatus according to claim 1,wherein the M sensors are disposed at regular intervals in thecircumferential direction.
 7. The plasma processing apparatus accordingto claim 1, wherein the plurality of gas supply nozzles and the Msensors are provided at the same height.
 8. The plasma processingapparatus according to claim 7, wherein the M sensors are provided atthe same height ranging from −10 mm to 80 mm in a vertical directionfrom a surface of a placement table on which a workpiece is placed inthe processing container.
 9. The plasma processing apparatus accordingto claim 1, wherein the plurality of gas supply nozzles and the Msensors are provided at different heights.
 10. The plasma processingapparatus according to claim 1, wherein the M sensors are disposed atpositions symmetrical with respect to positions of the N microwaveintroducing modules disposed at regular intervals on the ceiling plateof the processing container based on a central axis of the processingcontainer.
 11. A method of controlling plasma using a plasma processingapparatus including: a plurality of gas supply nozzles which areprovided on a wall surface of a processing container and supply processgas toward an inside of the processing container in a radial direction;N microwave introducing modules disposed in a circumferential directionof a ceiling plate of the processing container so as to introducemicrowaves for generating plasma into the processing container, whereinN≥2; and M sensors provided on the wall surface of the processingcontainer so as to monitor electron density Ne and electron temperatureTe of the plasma generated in the processing container, wherein M equalsto N or a multiple of N, the method comprising: controlling at least anyone of power of the microwaves introduced from the microwave introducingmodules and a phase of the microwaves introduced from the microwaveintroducing modules based on at least any one of the electron density Neand the electron temperature Te of the plasma monitored by the sensors.